1. Field of Technology
This application generally relates to methods for making concentrated aqueous solutions including high concentrations of dissolved magnesium chloride. This application also relates to methods for utilizing anhydrous magnesium chloride and other solid by-products of the Kroll process, which is conventionally used to make metallic titanium, zirconium, and hafnium.
2. Description of the Background of the Technology
A brine is a concentrated salt solution, e.g., a concentrated aqueous solution of sodium chloride or magnesium chloride (MgCl2). Magnesium chloride brine may be used as, for example, a de-icer, an anti-icer, or a dust suppressant. Commercial magnesium chloride brines commonly contain about 30 weight percent of magnesium chloride. Magnesium chloride may form various hydrates having the general formula MgCl2.(H2O)x when dissolved in water. Commercial brines comprising hydrated magnesium salts also may include toxic and/or corrosive impurities. Removing the impurities may be expensive and require complex processing. Therefore, industrial production of magnesium chloride brines including low levels of toxic and/or corrosive impurities is of significant commercial interest.
The Kroll process may be used to make metallic titanium, zirconium, and hafnium from certain ores. Metallic titanium, for example, may be manufactured by purifying titanium dioxide ore, chlorinating the refined ore to form titanium tetrachloride in the presence of magnesium or another reducing agent, and reducing the titanium tetrachloride to metallic titanium in a neutral argon or helium atmosphere. This process may be represented by the following equation:TiCl4(g)+2Mg(l)→Ti(s)+2MgCl2(l)[T=800-950° C.]
The Kroll process produces titanium in the form of a porous metallic titanium sponge and a solid material by-product that includes solid anhydrous magnesium chloride and metal solids, such as titanium and magnesium. The anhydrous magnesium chloride produced as a by-product of the Kroll process may include a reduced concentration of toxic and/or corrosive impurities compared to commercial brines comprising hydrated magnesium salts. Making magnesium chloride brine using conventional techniques from anhydrous magnesium chloride, however, is problematic because such conventional techniques involve special processing equipment and handling techniques. This is because if anhydrous magnesium chloride is contacted with water in the prescribed ratio for 30% brine, the temperature of the mixture increases rapidly to 130° C., the boiling temperature of the brine, and vigorously generates steam. Indeed, the solid material by-product of the Kroll process is characterized as a hazardous waste because of the exothermic dissolution of the anhydrous magnesium salt in water, as well as the pyrophoric hazard of the metal solids and the possible generation of hydrogen gas from the reaction of excess magnesium with water.
Therefore, it would be advantageous to provide more commercially viable and cost-effective methods of making brines from anhydrous magnesium chloride.